Push back storage racks are extensively utilized in warehouses and the like for storage of loads, such as palletized loads. Such storage racks typically permit at least two and quite conventionally three such loads to be stored generally horizontally in adjacent front-to-back relationship. The loads are all moved into and out of the storage rack from a front end thereof. Accordingly, the storage rack typically employs a frame which includes a pair of support tracks which are sidewardly-spaced and extend longitudinally along a storage bay, with the tracks being slightly downwardly sloped as they project forwardly. A primary load-supporting carriage, as well as at least one secondary such carriage, are typically rollingly supported on the tracks, with the primary carriage and its load being stored in a rearward-most position, the secondary carriage and its load being stored in an intermediate position, and a further load being stored directly on the tracks or on the frame in a front position. The primary and secondary carriages are constructed such that the primary carriage normally overlaps or telescopes over the secondary carriage so that both can be stored adjacent the front position of the storage rack when the rack is empty or has only a single load therein, the latter being supported on the primary carriage. When a second load is moved into the storage bay, it is moved inwardly to engage and push the first load and the primary carriage rearwardly to the intermediate position, with the second load being deposited on the secondary carriage. A third load is then similarly inserted into the bay by engaging the load on the secondary carriage and pushing both carriages and their loads rearwardly so that the third load can be deposited directly on the tracks in the front position. Removal of the loads occurs in a reverse sequence, with the carriages moving by gravity downwardly along the tracks so as to return to the front position.
Numerous storage racks of this latter type have been constructed and are in use. Such racks typically utilize a track arrangement having different roller track surfaces for each of the carriages. For example, many of the known storage racks utilize tracks formed similar to I-beams, whereby the rollers for the secondary carriage engage the inner channel of the I-beams, and the rollers for the primary carriage engage the outer channel of the I-beams. With this arrangement, each carriage is also typically provided with four rollers, one being disposed adjacent each corner of the carriage, which rollers engage respective track surfaces. While such arrangements have proven to operate in a generally satisfactory manner, nevertheless the need for multiple track surfaces as a function of the number of carriages, as well as the need for four support rollers on each carriage, increases the overall structural and operational complexity, particularly with respect to the wear and contamination problems created by the additional rollers and specifically the additional exposed track surfaces.
Examples of push back storage racks, many having structural and functional relationships of the type described above, are shown by U.S. Pat. Nos. 4 988 251, 4 955 489, 5 203 464, 5 184 738, 4 949 852, 4 915 240, 4 773 546, 4 687 404, 4 613 270, 4 462 500 and 4 341 313.
Accordingly, it is an object of this invention to provide an improved push back storage rack which is believed to improve upon the structural and operation characteristics of such storage racks, and which is particularly believed to overcome disadvantages associated with prior racks of this general type, as briefly summarized above.
In the present invention, there is provided an improved push back storage rack for permitting at least three loads to be stored in generally horizontally adjacent relationship, such as in adjacent front-to-back relationship along a storage bay. The storage rack includes a frame on which a pair of generally sidewardly-spaced and parallel support tracks are fixedly mounted, which tracks preferably slope slightly downwardly as they project forwardly. A primary carriage is rollingly supported on the tracks and is adapted to have a first load supported thereon. The primary carriage is rollingly movable along the tracks into a rearward-most storage position. At least one secondary carriage is also provided and includes a front frame part provided with rollers which rollingly engage the tracks. The secondary carriages has cantilevered rearwardly projecting frame parts which are telescopically engaged and supported within side frame parts of the primary carriage, whereby the rear of the secondary carriage is supported directly by the primary carriage. With the secondary carriage extended outwardly from the primary carriage, a second load can be supported directly on the secondary carriage, the latter being positionable in an intermediate location along the front-to-back direction of the bay. A third load can be supported directly on the support tracks in a front position when the secondary and primary carriages and their loads are disposed respectively in the intermediate and rear positions. The carriages and their respective loads are moved forwardly into the front position due to the urging of gravity when the frontmost load is removed from the rack.
In the improved storage rack of this invention, as aforesaid, one or more secondary carriages can be provided, each being adapted to have its own load supported thereon. One secondary carriage is telescopically engaged with and projects forwardly from the rear carriage as described above, and the next secondary carriage is of generally the same construction as the first-mentioned secondary carriage but is telescopically engaged with and projects forwardly from the first-mentioned secondary carriage.
In the improved storage rack of this invention, as aforesaid, the carriages can be constructed efficiently and economically utilizing standard structural elements, such as conventional square or rectangular tubing, and at the same time the support tracks are provided with only a single pair of cooperating support surfaces for engagement with the rollers of all of the carriages. Additionally, the secondary carriage or carriages have rollers which engage the tracks only adjacent the front ends thereof, thereby minimizing the number of exposed rollers as well as minimizing the number of required tracks. At the same time the telescopic tubes which define the side rails of the various carriages, and the telescopic relationship therebetween, provides significant strength and rigidity while at the same time providing simple and lightweight structures.
Other objects and purposes of the invention will be apparent to persons familiar with racks of this general type upon reading the following specification and inspecting the accompanying drawings.